Published online by Cambridge University Press: 14 April 2009
An arg− conditionally Sm-dependent E. coli B strain became unable to grow on minimal agar containing low levels of Sm when the strain acquired an R factor which mediates Sm and Blu adenylation. The same R-containing strain, however, grew normally when Blu was substituted for Sm in the agar. The data strongly suggest that Sm-adenylate does not suppress the arg− phenotype in an in vivo system. The possibility that Blu-adenylate can cause phenotypic suppression without being bactericidal in vivo is discussed.